I. Field of the Invention
This invention relates to an improved process for laminating a discrete section of a photosensitive layer to at least one substrate and automatically trimming the laminated sections.
II. Description of the Prior Art
Typical of the prior art of laminating processes in which a relatively thin layer of material is applied to a relatively thick substrate are the U.S. patents to Del Bianco, U.S. Pat. No. 4,214,936, and to Gebrian et al, U.S. Pat. No. 4,495,014.
According to Del Bianco, a continuing series of panels to be laminated are advanced through succesive preparatory stations before laminating occurs. Each panel is preheated by rolls which advance the panels toward the nip of rolls which actually perform the lamination step. A sensor immediately upstream of the nip of the laminating rolls senses the leading and trailing edges of a panel to cause time delayed operation of the laminating rolls. This results in a discontinous operation with the stated desired result of uniformly spacing the resultant laminated panels from each other. As disclosed in Del Bianco, the laminating rolls remain closed at all times and rotate continuously while a panel is inserted between them. As a result, the entire length of a panel is laminated. Also, the rolls operate discontinuously. Once they start to rotate, they continue until the panel advances through and beyond them. Successive panels are loosely joined by an interconnecting length of film and no mechanism is disclosed for severing the film from the panel.
In Gebrian et al, a board to be laminated is heated, then advanced into the open nip of a pair of pressure rolls. A web of photosensitive film which includes a photosensitive layer coated on a carrier web is advanced from a feed roll to the open nip and over each pressure roll so that the photosensitive layer faces inward toward the advancing board. The pressure rolls are brought together at a specific distance behind the leading edge of the board to form a line of pressure perpendicular to the direction of advance. The board continues to advance through the closed nip and the photosensitive layer is laminated to the board surface until a second specified distance along the board is reached, at which time, with the board still advancing, the pressure rolls are separated and returned to the open nip configuration. The photosensitive layer is trimmed from the carrier web at the locations at which the lamination respectively begins and ends on the board. Each pressure roll for applying the photosensitive film is then reversed so that the terminal edge of the photosensitive film on the carrier web is returned to the nip of the pressure rolls for lamination on a subsquent board on a further surface of the same board to thereby avoid waste.
Prior Art having the general nature of the patents just described exhibit some drawbacks. For example, it often occurred that substrates operated on by prior art processes, when laminated, would exhibit a photosensitive layer having localized poor adhesion on the substrate resulting in ragged edges of the photosensitive layer along the line of demarcation at which the photosensitive layer is laminated to the substrate. In turn, small chips or flakes of the photosensitive layer then tend to break off and adhere to the surface of the laminated substrate at other locations. Such adherence at other locations will cause undesirable exposure variations during a later step which adversely affect the end product. Another drawback of prior art processes resided in the fact that they required greater spacing between successive substrates resulting in a lower production rate than desirable. This often resulted in wastage of photosensitive layer material. Since the photosensitive layer material generally continues to advance to the nip of the pressure rolls even when it extends between successive substrates, it follows that the greater the distance between successive substrates, the greater the wastage of the photosensitive layer material. Additionally, systems for performing prior art processes often lacked the ability to readily readjust so as to accomodate, as desired, different sizes of substrates and different sizes of placements of the photosensitive layer.
It was with knowledge of the current state of the art and in view of the problems previously encountered as noted above, that the present invention was conceived and has now been reduced to practice.